Difficult in nutshell. They try to check not just the depth of your knowledge, but also the ways in which you apply that knowledge to solve real world problems. This is something which most candidates cannot do. Thus, end up feeling more difficult than it has to be.
Other Product Manager Interview Reviews for Google
Very self-driven, first of multiple rounds, where I had to take the initiative to arrive at the problem, constraints, approach, solutions, tradeoffs and reasoning behind it in a matter of 30 minutes.
You would have to do a hiring assessment first, then a recruiter screening follows. First round interview with the hiring manager. Majorly product sense and product improvement. The questions were not direct though.
Overall a lot of steps to the interview process. Talked to different people and had opportunities to ask questions. Many different stages which made it a lengthy process overall. Wasn't too bad.